1. Field of the Invention
This invention relates to a hitching mechanism for connecting two pieces of large equipment, and in particular, to a hitching mechanism that is operable from a location remote from the area of connection. Although the hitching mechanism of the invention can be used to connect a variety of machines or equipment, it will find its greatest use in paving operations, and more particularly, with the connection of a windrow elevator machine to a paving machine.
2. Description of the Background Art
Paving operations, including the pavement of roadways, parking lots, and the like, play an important part in today's transportation network. Most paving operations proceed by preparing a flat surface on the ground and then depositing, spreading, leveling and compacting a pavement material such as asphalt, gravel, cementitious aggregate mixes, and the like, over the prepared surface. To assist in such a process, many paving operations employ a paving machine such as PF-510 paver, commercially available from BlawKnox. Such a paver is a self-propelled machine having a hopper for receiving the pavement material. The pavement material is fed from the hopper to a screed which deposits the material on the prepared surface. As the paver is advanced, the material is spread, compacted and leveled by the paver to provide a uniform and durable surface.
When performing such a paving operation, the pavement material needs to be transported from a supply location and delivered to the paver's hopper. In one approach to filling the hopper, a rear dump truck is employed to transport the pavement material from the supply location and to the paver's receiving hopper. Because of the costs involved in filling the paver in such a manner, alternative procedures have been prepared to fill the paver's hopper. In one alternative procedure, the pavement material is delivered from the supply location in a bottom-dump trailer which dumps the pavement material in a windrow on the prepared surface ahead of the paver. To transfer the windrow of material into the paver's receiver hopper, a windrow elevator machine, such as a 660-H elevator machine, commercially available from Lincoln Manufacturing, is employed. The windrow elevator machine is pushed by the paver along the windrow of material to gather and lift the material directly into the receiving hopper of the paver.
An exemplary windrow elevator machine 10 is shown in FIG. 1. The elevator machine 10 includes an elevator chain 12 that is powered by a hydraulic system for transporting the windrow of pavement material from the ground and into the receiver hopper of the paver. As the elevator machine 10 is pushed by the paver, the windrow of material is scooped onto the elevator chain 12 at a front end 14 where it is elevated to a back end 16 and dropped into the paver's receiver hopper.
To provide a connection between the elevator machine 10 and the paver, the elevator machine 10 is provided with a pair of metal plates 18, 20 that are connected to a frame 21 at the back end 16. Each of the plates 18, 20 is provided with vertical elongate slot 22 and 24, respectively, for connecting a paving machine 36 (see FIG. 2). Shown in FIG. 2 is one embodiment of a conventional paving machine 36 having one type of a prior art connector for connecting the paving machine 36 to the paver 10. Other types of connectors exist which operate in a similar manner. The paving machine 36 includes a first pair of spaced-apart ears 30 and a second pair of spaced-apart ears 32. The pairs of ears 30, 32 are bolted to a front end 34 of the paving machine 36 and are provided with holes 31 for receiving pins 26, 28. To connect the paving machine 36 to the elevator machine 10, the paving machine 36 is advanced toward the elevator machine 10 until the plates 18, 20 are receiving between each of the ear pairs 30 and 32 and until the holes 31 are aligned with the slots 22 and 24. A worker is then positioned between the elevator machine 10 and the paving machine 36 to manually slide the pins 26, 28 through the holes 31 of each of the ear pairs 30, 32 and through the aligned elongate slots 22, 24, thereby providing a connection between the two machines 10, 36.
Connecting the elevator machine 10 to the paving machine 36 in this manner or a similar manner suffers from a number of serious drawbacks. For example, aligning the pairs of ears 30, 32 with the plates 18, 20 when advancing the paving machine 36 toward the elevator machine 10 is difficult and time-consuming. Furthermore, once the plates 18, 20 are received between the ears of each of the ear pairs 30, 32, further alignment is often necessary so that both pins 26, 28 can manually be inserted through both the holes 31 and the slots 22, 24. In a similar manner, separation of the machines 10, 36 can be difficult and time-consuming if the machines 10, 36 are not properly aligned. Improper alignment causes binding of the pins 26, 28 in the slots 22, 24, making their removal difficult, if not impossible, until the machines 10, 36 are properly realigned.
In another drawback, the prior art hitching arrangement illustrated in FIG. 2 provides a generally inflexible connection and therefore does not adequately account for ground height variations negotiated in many paving operations. Because of the inflexibility of the prior art hitch, operation of the machines 10, 36 on vertical offsetting surfaces often places an unacceptable and destructive load on one or both of the machines 10, 36. For example, a bridge deck surface can be located vertically above the roadway subgrade by about 10 inches or more. When negotiating such a bridge deck surface, the elevator machine 10 becomes vertically offset from the paving machine 36 thereby binding the pins 26, 28 in the slots 22, 24 and unduly stressing the frames of the machines 10, 36. Such stresses can easily reach or exceed their mechanical limits resulting in costly damage to the machines 10, 36.
Another drawback arises by requiring a worker to stand between the machines 10, 36 to insert or remove the pins 26, 28, sometimes placing the worker out of view of the paving machine operator. Serious injury could result to the worker in the unlikely event that safety procedures are violated causing accidental movement of the paving machine 36 with the worker positioned between the machines 10, 36.
Still another drawback is the manner in which the pairs of ears 30, 32 are connected to the paving machine 36. Usually, the pairs of ears 30, 32 are bolted to the paving machine 36 and are sized to mate only with a particular type of elevator machine. Hence, if the paving machine 36 is used with another piece of equipment (such as when filling the paving machine 36 with materials delivered from a rear dump truck), the pairs of ears 30, 32 must be unbolted from the paving machine 36 to accommodate the equipment used in the alternative feed method. The time and difficulty required to make such a change often discourages separation of the machines 10, 36 during ongoing paving operations, thereby limiting potential utilization of the bottom-dump transport and delivery procedure and increasing costs. In a further drawback, mounting of the pairs of ears 30, 32 to the paving machine 36 can require expensive modifications to the paving machine 36.
It would therefore be desirable to provide a hitching mechanism that would overcome or greatly reduce these and other problems. The hitching mechanism should allow for the easy and efficient connection of the two machines while at the same time reducing the risk of injury to the workers involved. In a particular aspect, the hitch should allow for the machines to negotiate surfaces having varied heights without placing excessive loads on either of the machines. The hitch should further allow for the accommodation of various makes and models of paving machines without complex or costly modifications to the paving machines. In still a further aspect, the hitch should allow for easy connection and removal of the machines so that different combinations of paving procedures are not discouraged.